Why does wp_customizer default values do not apply when theme is installed for the first time?

No, there is no automatic way to save all defaults, and for good reason. It avoids cluttering the database with unnecessary values, and allows themes to actually change their defaults down the line.
Instead of trying to save all defaults, just change all your calls to get_theme_mod to include the default value as the 2nd parameter. That is how it is intended to be used 🙂

Related Posts:

  1. How do I remove a pre-existing customizer setting?
  2. Custom Image section in Customizer
  3. Get entered value of customiser field for live preview
  4. How to remove the Theme Customization Button from the dashboard and themes options page?
  5. Allow Shortcode in Theme Customizer
  6. Theme Customizer – Nested Sections?
  7. Trigger Customizer saving process with Javascript only
  8. WordPress Customizer Typography: How to load just the unique Google Fonts?
  9. Can we add more than one control under a setting in WP theme customizer?
  10. Widgets panel not displaying in the Theme Customizer
  11. Is it possible to display the admin bar while in the Theme Customizer?
  12. How to Change CSS Variable value in Theme Customizer Live Preview
  13. How to remove menus section from WordPress theme customizer
  14. Get background color for Live Preview with Theme Customization API?
  15. Checking if there is an Image inserted – if not don’t display anything
  16. Default header image does not display
  17. WordPress Customizer Control with React
  18. Responsive Images – Generating multiple images from Theme Customizer control upload?
  19. Modify Javascript Configuration Options for Theme Customizer Colour Picker
  20. Modify the Additional CSS section (adding a disclaimer)
  21. Theme Customizer – Choose where widget area appears, to let users organise widgets
  22. wordpress custom theme import and export options for sample data [closed]
  23. How to hook CSS file according to theme selection in the customizer section
  24. How Can I Create a List of Values to Be Iterated Through via WordPress Customization API?
  25. Custom Script Section Only Echoes Text
  26. How to disable automatic colors in the Twenty Twenty theme?
  27. WordPress not registering Theme Customization Section
  28. WP Customize refresh problem
  29. Input ordering in wordpress theme customizer
  30. How to add new args data in $wp_customize->add_setting?
  31. Hide header texts (Title & Tagline) in custom-header.php
  32. get_option in header.php not returning value from customizer
  33. Internal error 500 accessing Theme > Customize
  34. Customizer: Unique identifier that distinguishes which image upload control is uploading an image
  35. Using an if statement in the theme customizer page
  36. How do i make a custom section’s setting display the default value in Customizer?
  37. How to add styles set by user in the customizer
  38. JavaScript stops working on selectively refreshed sections one inside the other
  39. Folder name for a pro version of a WordPress.org theme?
  40. Display theme layouts [closed]
  41. “Add A Widget” button in the Customizer
  42. Can I add multiple arrays within add_theme_support( ‘colors’ )?
  43. Customizer: save setting/control content to post/page
  44. Using WordPress’ Theme Customizer to select page templates that update layout in the preview
  45. Is accessing theme and using customizer GPL distribution?
  46. How to disable wordpress from overload my stylesheet styles with customizer styles
  47. How to enqueue javascript for WP Customize options sidebar?
  48. Is it possible to visually group items on the theme customizer?
  49. Theme Customizer not loading JS for live preview
  50. Customizer – loading settings/controls/sections/panels based on a id/page id
  51. Change WordPress header color using customizer
  52. Default Text not showing from customizer
  53. Is there any way to register custom background images like header images?
  54. How to transfer one domain to another domain without losing theme options (customizer)?
  55. Theme Customizer not displaying saved values in wp_head (CSS)
  56. Is there a WordPress boolean for “theme_customizer_active()”?
  57. How to allow certain PHP functions when using sanitize_callback in the word press customizer
  58. Customizer Color Control Not Working
  59. where is real values of variables?
  60. How to allow users to create their own website within my domain? [closed]
  61. How to set Post meta-box defaults based on the choices made by user in Customizer?
  62. Avada Child Theme Development
  63. Questions from a new WP Dev [closed]
  64. Adding a new setting using Kirki or WP customizer with an if statement
  65. Theme customizer – can’t add section/settings
  66. Create something that can be added or removed in Customizer
  67. add shortcode support in customizer
  68. Customize Option Framework
  69. How to set a custom URL for the iframe in the customize page
  70. How to add wysiwyg editor in customize screen using customize_register
  71. How to register dynamic settings in WordPress Customizer?
  72. How to copy page/post from one theme to another?
  73. How to change listing type permlink?
  74. In wordpress customizer div still showing even if I hid it with javascript
  75. How to enable admin to upload multiple images to support header carousel slider theme in WordPress?
  76. Removing element from DOM with jquery through plugin Custom Scripts for Customizer
  77. Image cropping isn’t working correctly when using Offload Media
  78. WordPress Custom Theme : Theme Builder vs ACF vs Gutenberg
  79. Fatal error: Class WP_Customize_Image_Control not found
  80. How do I remove header/page-title image in farvis theme? [closed]
  81. Duplicate child theme incl. design changes
  82. Styling the website via the customizer – do the changes stay after theme update?
  83. Is there a way to create sections under “Colors” panel in the Theme Customizer?
  84. How to toggle WP Customizer Panel and Section with JavaScript API?
  85. Debugging slow WordPress Theme Customizer (Any option similar to Query Monitor)?
  86. How to customize the colors within a stylesheet using a WordPress setting
  87. Add multiple sections, settings and controls at once to the Customizer
  88. How to fix an issue with customizer live preview?
  89. How to create multiple customizer controls in one control
  90. Editable screenshot.png in a custom theme developed
  91. WordPress Customization API overwrite LESS variable
  92. Using Customizer value in an external PHP file inside a theme
  93. get_theme_mod not pulling css colors into header using wp_head
  94. Customizer API way function is_customize_preview() works only in main page?
  95. Theme customizer live preview JS- Trying to bind to an html image url without luck
  96. trying to figure out how to use more that one image upload in the same section in theme customizer
  97. My theme is full of error messages in the “Customize” screen, but nowhere else
  98. How to show associated fields if checkbox is checked in customize widget screen using wp_customize?
  99. WP Customizer get control value on change
  100. Execute javscript when theme customizer loads (autosave issue)